Motor brush



W. H. KITTO MOTOR BRUSH Feb. 20, 1934.

Filed Aug. 20, 1932 INVENTOR ATTORNEY Patented Feb. 20, 1934 PATENT OFFICE MOTOR BRUSH William H.

Hoover Company, poration of Ohio The present invention relates to motor brushes for electric motors and generators. More speciiically the invention comprises an improved mounting for a current-carrying brush in an electric motor or generator which is so constructed that it insures the operation of the brush during its effective life and, of greater importance, it eliminates any danger of commutator shorting or burning through the undesirable contact therewith of parts of the brush mounting after the brush is worn away.

It is an object of the present invention to provide a new and improved electric brush mounting. It is a further object to provide an improved mounting for an electric current-carrying brush in which improved means are provided to urge the brush into contact with the commutator or slip rings. A still further object is the provision of an improved mounting for an electric currentcarrying brush in which a resilient spring is provided to urge the brush into contact with the commutator or slip rings, which spring is so constructed that it cooperates with other parts of the mounting to prevent its own extension thru the mounting into contact with the commutator or slip ring. These and other more speciiic objects will appear upon reading the following specification and claim and upon considering in connection therewith the attached drawing to which they relate.

In the drawing in which the preferred embodiment of the present invention is disclosed:

Figure 1 shows in section a ,brush mounting constructed in accordance with the present invention embodied in a motor;

Figure 2 is a section thru the mounting shown in Figure 1 taken at right angles to the section there shown and further being a section upon the line 2--2 of Figure 4;

Figure 3 is an exploded tion shown in Figure 2;

Figure 4 is a view looking in the direction of the arrows upon the line 4-4 of Figure 1;

Figure 5 is a section thru a modied construction oi the present invention;

Figure 6 is a section taken of Figure 5.

In Figure 1 of the drawing the brush mounting constructed in accordance with the present invention is shown positioned in an electric motor, the outer casngof whichis indicated generally by the reference character i, the stator frame by the reference character 2, the stationary eld which is mounted upon the frame 2 by the reference character 3. the shaft 5, on which is carried view of the construcupon' the line 6-6 Kitto, Canton, Ohio,

North Canton, Ohio, a corassignor to The Application August 20, 1932. Serial No. 629,676

(Cl. P11-324) the armature 6 and the commutator 7, being carried in suitable bearings 8 and 9 in the frame 2. The electric current-carrying brush which contacts the conmiutator 'I is indicated by the reference character 10 and it is in the mounting and 60 means for maintaining this brush in contact with the commutator 'I that the present invention lies.

Frame 2 is shown to be provided with a seat which is indicated by the reference character-11. Within this seat are secured, by means of the set screw 12, the brush holder 13 and its surrounding insulator 14. Brush 10 is slidingly seated by the inner end of holder 13, as is clearly shown in Figures 1, 2 and 4, the extreme inner end of the holder being reduced for an appreciable distance, 7o as indicated at 15, so that it closely encloses the brush. It is to this reduced portion that the current-carrying lead 16 is attached by the clip 17. Immediately behind the reduced portion 15 of metallic holder 13 are positioned the shoul- 75 ders 18. 18 etc. formed by the enlargement o! the central parts of the sides of the rec ar portion l5, which enlargements extend for an appreciable distance toward the outer end of the brush. The enlargements are just sulcient 30 to permit the passage of the spring 19, hereinafter more fully described, at its point of greatest diameter.

In order that the current-carrying brush will be maintained at all times in proper contact with g5 the commutator 'I to which it must deliver current in the operation o! the machine a resilient spiral spring 19 is provided which encioses and seats on the outer end of brush l0 which is shaped in a well known manner to receive it. 'Ihis spring, 90 at its outer end contacts the removable cap 20 which is formed oi suitable insulating material which seats in screw threaded relation with the interior of member 13, there being provided a rubber insulating washer 22 between the cap and the holder.

Spring 19 is shaped in a particular manner for a very dennite purpose. A short distance outwardly from its point of seating upon the brush the spring is provided with an enlarged turn l winch is indicated at 23. This turn is greater in its cross sectional dimensions than the brush to dennitely limit the penetral when that member has forced brush 20 to such a distance towards commutator 'I that turn 23 contacts the shoulders 18, 18. This relationship produces a desirable functional result. In the operation of the motor the brush 10 is gradually worn away and is consequently u.

moved toward the If this commutator by the spring. process were allowed to continue indefinitely' the brush 10 would eventually be completely worn away and the inner end of spring 19 would contact the surface of the commutator, resulting in sparking and burning of that member. With spring 19 constructedas described the possibility of its contacting the surface of the commutator after the brush is worn away is yabsolutely eliminated. The shoulders 18, 18 are so positioned that the brush 10 is allowed to be worn and moved toward the commutator until it is so short that further 4decrease in its length would result in instability. When this condition has been reached the brush must be replaced.

In Figures 5 and 6 a modication of the invention aforedescribed is disclosed. In this construction the reduced portion 15 has been shortened and the shoulders 18,v 18 etc. have been positioned further inwardly in the holder 13. The spring 19 is enlarged at its very front end, as indicated at 24, instead of at a distance in the rear of the brush as in the first embodiment. This construction performs exactly as that xst described, the enlarged turn 24 seating against the inner end of the reduced portion 15 o1' the holder to limit spring movement.

I claim:

An electric motor brush mounting construction including a brush holder open at itsends, removable closure means closing one end of said holder, a current-carrying brush slidably positioned in said holder and extended from the other end thereof, a spiral spring extending between said closure means and said brush exerting a force to urge said brush through said holder, said spring being formed to extend to a greater-than-normal diameter at one point, and means on said holder extended inwardly to contact said spring at said point to limit its movement in said holder, said spring being of such length from said point to said brush that it does not extend beyond the end of said brush holder.

WILLIAM H. KI'ITO. 

